In the past, a number of techniques have been employed in order to provide a permanent record of an image from information existing as electrical signals. One popular technique employs a cursor, or beam of light, traveling in a raster across a record medium, and selectively creating light and dark spots on that medium the composite of which form visible images of character representations. This technique has been used in conventional copying machines.
While character generators of the type described have been operated under the control of a digital processor in the past, the extent of this control has been governed manually by an operator who is in a position to observe both the input to the digital processor and the output from it. However, unique problems arise when the input and output functions are not under centralized control. In such situations, for example in instances where data is to be transmitted from a remote location to produce an image on record media of the type described, conventional record transcription systems are likely to become overloaded and thus data will be lost. While the most apparent solution to this problem would be merely to increase the memory capacity and sophistication of the digital processor utilized, the necessary expense of the added data storage requirement and data processing capability is prohibitive for many printing installations. Accordingly, the present invention has been devised to allow data to be produced and directed to a printing mechanism without commonality of control of the data processor and the printing mechanism, and without requiring a high degree of digital processor involvement in the print operation. Pursuant to this objective, the concept of the interface apparatus of the present invention has been employed.
More specifically, it is an object of the present invention to provide a message interface for receiving message information in digitized form that is not maintained in a permanent digital memory, and to transcribe this information into a pattern of light and dark areas on a record medium to produce a visible record of the message.
A related object of the invention is to reduce the sophistication and the storage capacity necessary for programmed instructions to a digital computer, and also to reduce the requirement for storage capacity in the computer which must be utilized to accomodate the programming for the printing operation. Thus, the computer need not be programmed to store message data and arrange for it to be printed as a printer becomes available. In this way very large expenditures in software programming and requisite computer storage capacity are eliminated.
A further object of the invention is to provide an interface unit that only processes transient message information for recordation as an image in permanent form, but that also retains and reproduces in visible form recurring caption or header information. While the permanent record media utilized could be previously imprinted with caption information if only a single standard format of such caption information were to be required, there is presently no acceptable procedure for calling forth only one of several caption information formats which recur on a regular basis without dedicating a large block of computer storage capacity to this function. By utilizing the present invention, however, trigger signals from a digital processor result in the generation of a complete array of caption information from the interface unit.
A related object of the invention is to allow a plurality of particular subsets of caption information to be reproduced on a visible record medium without the requirement for computer programs to devise print format information or to select such information from computer memory.